The cat has long been a standard preparation for anatomical and acute physiological studies of muscle function and motor control at the spinal cord level. In this project, a wide variety of traditional and novel kinesiological techniques are being used to study the performance of motor tasks in unanesthetized, normally behaving cats. Techniques now in use include computer-aided reconstruction of skeletal movement from videotape, multi-axis force plates, and chronically implanted microelectrodes, nerve cuff and EMG electrodes, and strain and length transducers. The major focus has been the study of hindlimb muscles and their afferent and efferent control during walking. Other hindlimb movements studied include jumping, paw shaking, scratching, and reflexes to cutaneous nerve stimulation. A new study involves recording simultaneously from a large number of sites in the various neck muscles subserving head and scapular motion during normal movements such as eating, grooming, visual tracking, and locomotion. The major objective is to correlate patterns of usage with the complex mechanics and compartmentalization and proprioceptive splecializations of these muscles. A major theme emerging from these experiments is a concept of "Task Groups," which denotes the segregation and specialization of sensorimotor systems to perform kinematically homogeneous tasks in an optimal manner. In particular, it seems likely that groups of alpha and gamma motoneurons and related muscle spindles and their afferents are recruited specifically to highly diverse tasks (e.g. active shortening vs. active lengthening), its pool of motor units is divided into independent groups which presumably employ different control programs optimal for each particular task. Future work will ask how well these notions extend to other bifunctional muscles and will examine how much anatomical and physiological independence exists between task groups.